The EUROHIS project has focused on the comparability of health surveys and has uncovered some of the problems that arise when attempts are made to compare data from different countries. Of course, similar problems of cross-cultural comparability also arise when comparing data from other sources, such as health registers, and are just as complex and difficult to tackle. One of the main advantages of health surveys, however, is the relatively low cost and time involved in adapting them according to the needs of health policy-makers. The output from the EUROHIS project provides researchers and policy-makers with a set of recommended common instruments for the measurement of eight health indicators. The development of these instruments has required careful consideration of relevant common concepts and how these should be defined and operationalized. The instruments are freely available for use by all countries, with the aim of enhancing national health information systems and facilitating cross-national comparisons of health data.